This invention relates to digital magnetic recording systems, especially for high density recording, such as is used for example with magnetic-disc devices.
The magnetic recording process can be divided into two parts, which in a digital context are usually called the write process and the read process. In high-density digital recording the write process normally records the digital information as a sequence of transitions between regions of a magnetic medium that are approximately fully magnetised in opposite senses. This process exploits the non-linear recording properties of the medium and allows transitions to be written very close together. There are no corresponding non linearities in the read process, so the read pulses resulting from neighbouring transitions will, as the transitions are brought closer together, overlap and superpose. This process, which will be referred to herein as "interference," makes it difficult to distinguish the individual pulses and recover the recorded information. It is therefore possible to write transitions closer together than they can be resolved by the read process.
The read process is therefore the factor which limits the density with which information can be recorded. If it could be improved the storage capacity of the medium and the rate at which data can be read out could be increased.